Method and apparatus for estimating battery state of health

ABSTRACT

Estimating a battery state of health (SOH) is described. The state of heath is estimated by obtaining a partial charge or discharge capacity of a target battery in a state of charge (SOC) interval of each of a plurality of SOCs. First dV/dSOC data is separately calculated for each SOC in an m th  preset battery capacity based on the m th  preset battery capacity and the partial charge or discharge capacity in the SOC interval of each SOC. A smallest overall dV/dSOC data deviation is determined from all overall dV/dSOC data deviations corresponding to M preset battery capacities. A preset battery capacity is determined corresponding to the smallest overall dV/dSOC data deviation as a retention capacity of an aged target battery. The retention capacity of the aged target battery is divided by a retention capacity of the target battery in a new battery state, to obtain the SOH estimate of the target battery.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/657,651, filed on Oct. 18, 2019, which is a continuation ofInternational Patent Application No. PCT/CN2017/087564, filed on Jun. 8,2017, which claims priority to Chinese Patent Application No.201710254759.6, filed on Apr. 18, 2017. The disclosures of theaforementioned applications are hereby incorporated by reference intheir entireties.

TECHNICAL FIELD

This application relates to the field of battery managementtechnologies, and in particular, to a method and an apparatus forestimating a battery state of health (SOH).

BACKGROUND

With development of society, batteries are more widely used in variousmobile or fixed devices, such as electric vehicles. A battery SOH is animportant parameter for evaluating a battery management system.Therefore, how to estimate the battery SOH becomes a hot topicresearched in industry.

In some current methods for estimating a battery SOH, a percentage of aretention capacity of an aged battery in a capacity of a battery in anewbattery state is defined as a battery SOH. When the retention capacityof the aged battery is determined, the parameter usually can be obtainedonly by performing one full charge or full discharge test. However, inconsideration of safe usage, the battery usually cannot be fullycharged/fully discharged. In addition, due to a difference betweenindividuals in a battery pack, it is more unable to ensure that allbatteries are fully charged/fully discharged. Therefore, it is difficultto evaluate the battery SOH because the foregoing implementationcondition for determining the retention capacity of the aged battery isrelatively harsh.

SUMMARY

Embodiments of this application provide a method and an apparatus forestimating a battery SOH, to resolve a current problem that duringevaluation of a battery SOH, it is difficult to evaluate the battery SOHbecause a retention capacity of an aged battery needs to be determinedbased on full charging/full discharging of a battery.

To achieve the foregoing objective, the embodiments of this applicationprovide the following technical solutions:

According to a first aspect, an embodiment of this application providesa method for estimating a battery state of health (SOH). The methodincludes: obtaining a partial charge or discharge capacity of a targetbattery in a state of charge (SOC) interval of each of a plurality ofstates of charge (SOCs), where the SOC interval of each SOC is aninterval whose start SOC is the SOC and whose length is dSOC; whendetermining that there are M preset battery capacities, separatelycalculating, according to steps S1 to S3, an overall dV/dSOC datadeviation corresponding to each preset battery capacity, where M is apositive integer: S1. separately calculating first dV/dSOC data of eachSOC in an m^(th) preset battery capacity based on the m^(th) presetbattery capacity and the partial charge or discharge capacity in the SOCinterval of each SOC, where m is a positive integer less than or equalto M; S2. separately calculating, based on a prestored dV/dSOCcharacteristic function, second dV/dSOC data corresponding to each SOC,where the dV/dSOC characteristic function is obtained by charging ordischarging the target battery based on a preset current in a newbattery state, the preset current is not greater than 1/20 Q_(BOL), andQ_(BOL) indicates a retention capacity of the target battery in the newbattery state; and S3. calculating an m^(th) overall dV/dSOC datadeviation of the plurality of SOCs based on the first dV/dSOC data ofeach SOC in the m^(th) preset battery capacity and the second dV/dSOCdata corresponding to each SOC; determining a smallest overall dV/dSOCdata deviation from all overall dV/dSOC data deviations; determining apreset battery capacity corresponding to the smallest overall dV/dSOCdata deviation as a retention capacity of an aged target battery; anddividing the retention capacity of the aged target battery by theretention capacity of the target battery in the new battery state, toobtain an SOH of the target battery. In other words, in this solution,the retention capacity of the aged target battery is estimated based onthe partial charge or discharge capacity in the SOC interval of eachSOC. In this way, this solution is unlike the prior art in which theparameter can be obtained only by performing one full charge or fulldischarge test, and therefore an implementation condition of thissolution is simpler and more flexible. In addition, this solution doesnot need to rely on historical data, and therefore is more robust.

In a possible design, the obtaining a partial charge or dischargecapacity of a target battery in a SOC interval of each of a plurality ofSOCs includes: obtaining the partial charge or discharge capacity of thetarget battery in the SOC interval of each of the plurality of SOCs withreference to the following first preset formula, where the first presetformula includes:

q_(SOC) _(n) =η∫_(SOC) _(n) _(−t) _(start) ^(SOC) ^(n) ^(−t) ^(end)i(t)SOC_(n)dt, where SOC_(n), represents an n^(th) SOC, q_(SOC) _(n)represents a partial charge or discharge capacity in a SOC interval ofSOC_(n), η is coulombic efficiency of the target battery, 0≤η≤1,SOC_(n)−t_(start), represents a start moment of the SOC interval ofSOC_(n), SOC_(n)−t_(end) represents an end moment of the SOC interval ofSOC_(n), and i(t)_(SOC) _(n) represents a random current in the SOCinterval of SOC_(n). Based on this solution, the partial charge ordischarge capacity of the target battery in the SOC interval of each ofthe plurality of SOCs can be obtained.

In a possible design, the separately calculating first dV/dSOC data ofeach SOC in an m^(th) preset battery capacity based on the m^(th) presetbattery capacity and the partial charge or discharge capacity in the SOCinterval of each SOC includes: separately calculating the first dV/dSOCdata of each SOC in the m^(th) preset battery capacity based on them^(th) preset battery capacity and the partial charge or dischargecapacity in the SOC interval of each SOC and with reference to a secondpreset formula, where the second preset formula includes:

${{g_{1}\left( {SOC}_{n} \right)} = {{Q_{m}\left( \frac{dV}{dq} \right)}_{SOC}}_{\;_{n}}},$

where Q_(m) represents the m^(th) preset battery capacity, SOC_(n)represents the n^(th) SOC, g₁(SOC_(n)) represents first dV/dSOC data ofSOC_(n) in the m^(th) preset battery capacity, V represents a voltage, qrepresents a partial charge or discharge capacity, and

$\left( \frac{dV}{dq} \right)_{{SOC}_{n}}$

represents

$\frac{dV}{dq}$

corresponding to SOC_(n). Based on this solution, the first dV/dSOC dataof each SOC in the m^(th) preset battery capacity can be calculated.

In a possible design, when the target battery works in a dischargestate, after the target battery is stable and static for a period oftime, or a working condition of the target battery keeps at a very smallcurrent for a period of time, it can be considered that batterypolarization disappears. In this case, a terminal voltage (V) of thetarget battery at an initial moment can be considered as an open circuitvoltage (OCV) of the target battery at the initial moment. In addition,because an OCV-SOC curve is linear in a short period of time, it can belearned that dq is proportional to dOCV in a short period of time.Therefore, when the target battery works in the discharge state, thesecond preset formula specifically includes:

${{g_{1}\left( {SOC}_{n} \right)} = {{Q_{m}\left( \frac{dV}{dq} \right)}_{{SOC}_{n}} = {Q_{m}\frac{{OCV}_{{SOC}_{n} - t_{end}} - {OCV}_{{SOC}_{n} - t_{start}}}{q_{{SOC}_{n}}^{\prime}}}}},$

where SOC_(n)−t_(start) represents the start moment of the SOC intervalof SOC_(n), SOC_(n)−t_(end) represents the end moment of the SOCinterval of SOC_(n), OCV_(SOC) _(n) _(−t) _(end) represents an OCV atSOC_(n)−t_(start), OCV_(SOC) _(n) _(−t) _(start) represents an OCV atSOC_(n)−t_(end), and q′_(SOC) _(n) represents a partial dischargecapacity in the SOC interval of SOC_(n).

In a possible design, the dV/dSOC characteristic function includes:

${{g_{0}\left( {SOC}_{n} \right)} = {a_{0} + {\sum\limits_{j = 1}^{6}\left( {{a_{j}*{\sin \left( {j*\omega*{SOC}_{n}} \right)}} + {b_{j}*{\cos \left( {j*\omega*{SOC}_{n}} \right)}}} \right)}}},$

where SOC_(n) represents the n^(th) SOC, SOC_(n) is an independentvariable of the dV/dSOC characteristic function, g₀(SOC_(n)) representssecond dV/dSOC data corresponding to SOC_(n), j represents an order, a₀,a_(j), and b_(j) are coefficients of terms, sin( ) represents a sinefunction, cos( ) represents a cosine function, and co representsfrequency. The dV/dSOC characteristic function provided in this solutionis a six-order Fourier function. To be specific, in this embodiment ofthis application, when the dV/dSOC characteristic function is fitted byusing a fitting tool, the fitting is performed on a basis that thecharacteristic function is the six-order Fourier function. Certainly, inpractice, the characteristic function may further include but is notlimited only to a polynomial function, a Fourier function, anexponential function, and the like. This is not specifically limited inthis embodiment of this application.

In a possible design, the calculating an m^(th) overall dV/dSOC datadeviation of the plurality of SOCs based on the first dV/dSOC data ofeach SOC in the m^(th) preset battery capacity and the second dV/dSOCdata corresponding to each SOC includes: calculating the m^(th) overalldV/dSOC data deviation of the plurality of SOCs based on the firstdV/dSOC data of each SOC in the m^(th) preset battery capacity and thesecond dV/dSOC data corresponding to each SOC and with reference to athird preset formula, where the third preset formula includes:

${G_{m} = {\sum\limits_{n = 1}^{N}\left( {{g_{0}\left( {SOC}_{n} \right)} - {g_{1}\left( {SOC}_{n} \right)}} \right)^{2}}},$

where N represents a quantity of SOCs, N is a positive integer not lessthan 2, SOC_(n) represents the n^(th) SOC, g₀(SOC_(n)) represents thesecond dV/dSOC data corresponding to SOC_(n), g₁(SOC_(n)) represents thefirst dV/dSOC data of SOC_(n) in the m^(th) preset battery capacity, andG_(m) represents the m^(th) overall dV/dSOC data deviation of theplurality of SOCs. Based on this solution, the m^(th) overall dV/dSOCdata deviation of the plurality of SOCs can be calculated.

According to a second aspect, an embodiment of this application providesan apparatus for estimating a battery SOH. The apparatus for estimatinga battery SOH has a function of implementing behavior in the foregoingmethod embodiment. The function may be implemented by hardware, or maybe implemented by hardware by executing corresponding software. Thehardware or the software includes one or more modules corresponding tothe foregoing function.

According to a third aspect, an embodiment of this application providesan apparatus for estimating a battery SOH, including a processor, amemory, a bus, and a communications interface. The memory is configuredto store a computer execution instruction. The processor is connected tothe memory by using the bus. When the apparatus for estimating a batterySOH runs, the processor executes the computer execution instructionstored in the memory, so that the apparatus for estimating a battery SOHperforms the method for estimating a battery SOH in any possible designof the first aspect.

According to a fourth aspect, an embodiment of this application providesa computer-readable storage medium, configured to store a computersoftware instruction used by the foregoing apparatus for estimating abattery SOH. When the computer software instruction runs on a computer,the computer can perform the method for estimating a battery SOH in anypossible design of the first aspect.

According to a fifth aspect, an embodiment of this application providesa computer program product that includes an instruction. When thecomputer program product runs on a computer, the computer can performthe method for estimating a battery SOH in any possible design of thefirst aspect.

For technical effects brought by any design manner of the second to thefourth aspects, refer to technical effects brought by different designmanners of the first aspect, and details are not described herein again.

According to a sixth aspect, an embodiment of this application disclosesa method for estimating a battery state of health (SOH). The methodincludes:

obtaining N states of charge (SOCs) of a target battery in N states,where the SOC is a ratio of a remaining capacity of the target batteryto a full charge capacity of the target battery; separately calculatingfirst dV/dSOC data of each SOC in an n^(th) state of charge based on acharge/discharge capacity of the target battery in the n^(th) SOC and anM^(th) preset capacity of the battery, where N represents a quantity ofSOCs, N is a positive integer not less than 2, n is a positive integerless than or equal to N, m is a positive integer from 1 to M, and M is aquantity of preset capacities; separately calculating, based on adV/dSOC-SOC characteristic function, second dV/dSOC data correspondingto each SOC, where the dV/dSOC-SOC characteristic function is obtainedby charging or discharging the target battery based on a preset currentin an new battery state, the preset current is not greater than 1/20Q_(BOL), and Q_(BOL) indicates a retention capacity of the targetbattery in the new battery state; obtaining an m^(th) overall dV/dSOCdata deviation of the plurality of SOCs through calculation based on thefirst dV/dSOC data of each SOC in the m^(th) preset battery capacity andthe second dV/dSOC data corresponding to each SOC; determining asmallest overall dV/dSOC data deviation from M overall dV/dSOC datadeviations; determining a preset battery capacity corresponding to thesmallest overall dV/dSOC data deviation as a retention capacity of anaged target battery; and obtaining an SOH of the target battery throughcalculation based on the retention capacity of the aged target battery.In this way, this solution is unlike the prior art in which theparameter can be obtained only by performing one full charge or fulldischarge test, and therefore an implementation condition of thissolution is simpler and more flexible. In addition, this solution doesnot need to rely on historical data, and therefore is more robust.

With reference to the sixth aspect, it should be noted that theobtaining an SOH of the target battery through calculation based on theretention capacity of the aged target battery includes: dividing theretention capacity of the aged target battery by the retention capacityof the target battery in the new battery state, to obtain the SOH of thetarget battery.

With reference to the sixth aspect, in a possible design, the methodfurther includes: obtaining a partial charge or discharge capacity ofthe target battery in a SOC interval of each SOC in the n^(th) SOC,where the SOC interval of each SOC is an interval whose start SOC is theSOC and whose length is dSOC, and the charge/discharge capacity in then^(th) SOC is a partial charge or discharge capacity in the interval.

Specifically, the obtaining a partial charge or discharge capacity ofthe target battery in a SOC interval of each SOC in the n^(th) SOCincludes:

obtaining the partial charge or discharge capacity of the target batteryin the SOC interval of each of the plurality of SOCs with reference tothe following first preset formula, where the first preset formulaincludes:

q_(SOC) _(n) =η∫_(SOC) _(n) _(−t) _(start) ^(SOC) ^(n) ^(−t) ^(end)i(t)SOC_(n)dt, where SOC_(n) represents the n^(th) SOC, q_(SOC) _(n)represents a partial charge or discharge capacity in a SOC interval ofSOC_(n), η is coulombic efficiency of the target battery, 0≤η≤1,SOC_(n)−t_(start) represents a start moment of the SOC interval ofSOC_(n), SOC_(n)−t_(end) represents an end moment of the SOC interval ofSOC_(n), and i(t)SOC_(n) represents a random current in the SOC intervalof SOC_(n).

With reference to the sixth aspect, the separately calculating firstdV/dSOC data of each SOC in an n^(th) state of charge based on acharge/discharge capacity of the target battery in the n^(th) SOC and anm^(th) preset capacity of the battery includes:

separately calculating the first dV/dSOC data of each SOC in the m^(th)preset battery capacity based on the m^(th) preset battery capacity andthe partial charge or discharge capacity in the SOC interval of each SOCand with reference to a second preset formula, where the second presetformula includes:

${{g_{1}\left( {SOC}_{n} \right)} = {Q_{m}\left( \frac{dV}{dq} \right)}_{{SOC}_{n}}},$

where Q_(m) represents the m^(th) preset battery capacity, SOC_(n)represents the n^(th) SOC, g₁(SOC_(n)) represents first dV/dSOC data ofSOC_(n) in the m^(th) preset battery capacity, V represents a voltage, qrepresents a partial charge or discharge capacity, and

$\left( \frac{dV}{dq} \right)_{{SOC}_{n}}$

represents

$\frac{dV}{dq}$

corresponding to SOC_(n).

When the target battery works in a discharge state, the second presetformula specifically includes:

${{g_{1}\left( {SOC}_{n} \right)} = {{Q_{m}\left( \frac{dV}{dq} \right)}_{{SOC}_{n}} = {Q_{m}\frac{{OCV}_{{SOC}_{n} - t_{end}} - {OCV}_{{SOC}_{n} - t_{start}}}{q_{{SOC}_{n}}^{\prime}}}}},$

where SOC_(n)−t_(start) represents the start moment of the SOC intervalof SOC_(n), SOC_(n)−t_(end) represents the end moment of the SOCinterval of SOC_(n), OCV_(SOC) _(n) _(−t) _(end) represents an OCV atSOC_(n)−t_(start), OCV_(SOC) _(n) _(−t) _(start) represents an OCV atSOC_(n)−t_(end), and q′_(SOC) represents a partial discharge capacity inthe SOC interval of SOC_(n).

In addition, it should be noted that the dV/dSOC-SOC characteristicfunction includes:

${{g_{0}\left( {SOC}_{n} \right)} = {a_{0} + {\sum\limits_{j = 1}^{6}\left( {{a_{j}*{\sin \left( {j*\omega*{SOC}_{n}} \right)}} + {b_{j}*{\cos \left( {j*\omega*{SOC}_{n}} \right)}}} \right)}}},$

where SOC_(n) represents the n^(th) SOC_(n) is an independent variableof the dV/dSOC-SOC characteristic function, g₀(SOC_(n)) representssecond dV/dSOC data corresponding to SOC_(n), j represents an order, a₀,a_(j), and b_(j) are coefficients of terms, sin( ) represents a sinefunction, cos( ) represents a cosine function, and co representsfrequency.

With reference to the sixth aspect, it should be noted that thecalculating an m^(th) overall dV/dSOC data deviation of the plurality ofSOCs based on the first dV/dSOC data of each SOC in the m^(th) presetbattery capacity and the second dV/dSOC data corresponding to each SOCincludes:

calculating the m^(th) overall dV/dSOC data deviation of the pluralityof SOCs based on the first dV/dSOC data of each SOC in the m^(th) presetbattery capacity and the second dV/dSOC data corresponding to each SOCand with reference to a third preset formula, where the third presetformula includes:

${G_{m} = {\sum\limits_{n = 1}^{N}\left( {{g_{0}\left( {SOC}_{n} \right)} - {g_{1}\left( {SOC}_{n} \right)}} \right)^{2}}},$

where N represents the quantity of SOCs, N is a positive integer notless than 2, SOC_(n) represents the n^(th) SOC, g₀(SOC) represents thesecond dV/dSOC data corresponding to SOC_(n), g₁(SOC_(n)) represents thefirst dV/dSOC data of SOC_(n) in the m^(th) preset battery capacity, andG_(m) represents the m^(th) overall dV/dSOC data deviation of theplurality of SOCs.

According to a seventh aspect, an embodiment of the present inventiondiscloses an apparatus for estimating a battery state of health (SOH).The apparatus includes an obtaining module and a calculation module,where the obtaining module obtains N states of charge (SOCs) of a targetbattery in N states, where the SOC is a ratio of a remaining capacity ofthe target battery to a full charge capacity of the target battery; andthe calculation module is configured to: separately calculate firstdV/dSOC data of each SOC in an n^(th) state of charge based on acharge/discharge capacity of the target battery in the n^(th) SOC and anm^(th) preset capacity of the battery, where N represents a quantity ofSOCs, N is a positive integer not less than 2, n is a positive integerless than or equal to N, m is a positive integer from 1 to M, and M is aquantity of preset capacities;

separately calculate, based on a dV/dSOC-SOC characteristic function,second dV/dSOC data corresponding to each SOC, where the dV/dSOC-SOCcharacteristic function is obtained by charging or discharging thetarget battery based on a preset current in an new battery state, thepreset current is not greater than 1/20 Q_(BOL), and Q_(BOL) indicates aretention capacity of the target battery in the new battery state;

obtain an m^(th) overall dV/dSOC data deviation of the plurality of SOCsthrough calculation based on the first dV/dSOC data of each SOC in them^(th) preset battery capacity and the second dV/dSOC data correspondingto each SOC;

determine a smallest overall dV/dSOC data deviation from M overalldV/dSOC data deviations;

determine a preset battery capacity corresponding to the smallestoverall dV/dSOC data deviation as a retention capacity of an aged targetbattery; and

obtain an SOH of the target battery through calculation based on theretention capacity of the aged target battery.

Optionally, the calculation module is specifically configured to dividethe retention capacity of the aged target battery by the retentioncapacity of the target battery in the new battery state, to obtain theSOH of the target battery.

With reference to the seventh aspect, the obtaining module is furtherconfigured to obtain a partial charge or discharge capacity of thetarget battery in a SOC interval of each SOC in the n^(th) SOC, wherethe SOC interval of each SOC is an interval whose start SOC is the SOCand whose length is dSOC, and the charge/discharge capacity in then^(th) SOC is a partial charge or discharge capacity in the interval.

With reference to the seventh aspect, optionally, the obtaining moduleis specifically configured to:

obtain the partial charge or discharge capacity of the target battery inthe SOC interval of each of the plurality of SOCs with reference to thefollowing first preset formula, where the first preset formula includes:

q_(SOC) _(n) =η∫_(SOC) _(n) _(−t) _(start) ^(SOC) ^(n) ^(−t) ^(end)i(t)SOC_(n)dt, where SOC_(n), represents the n^(th) SOC, q_(SOC) _(n)represents a partial charge or discharge capacity in a SOC interval ofSOC_(n), η is coulombic efficiency of the target battery, 0≤η≤1,SOC_(n)−t_(start) represents a start moment of the SOC interval ofSOC_(n), SOC_(n)−t_(end) represents an end moment of the SOC interval ofSOC_(n), and i(t)_(SOC) _(n) represents a random current in the SOCinterval of SOC_(n).

With reference to the seventh aspect, optionally, the calculation moduleis specifically configured to:

separately calculate the first dV/dSOC data of each SOC in the m^(th)preset battery capacity based on the m^(th) preset battery capacity andthe partial charge or discharge capacity in the SOC interval of each SOCand with reference to a second preset formula, where the second presetformula includes:

${{g_{1}\left( {SOC}_{n} \right)} = {Q_{m}\left( \frac{dV}{dq} \right)}_{{SOC}_{n}}},$

where Q_(m) represents the m^(th) preset battery capacity, SOC_(n)represents the n^(th) SOC, g₁(SOC_(n)) represents first dV/dSOC data ofSOC_(n) in the m^(th) preset battery capacity, V represents a voltage, qrepresents a partial charge or discharge capacity, and

$\left( \frac{dV}{dq} \right)_{{SOC}_{n}}$

represents

$\frac{dV}{dq}$

corresponding to SOC_(n).

It should be noted that, when the target battery works in a dischargestate, the second preset formula specifically includes:

${{g_{1}\left( {SOC}_{n} \right)} = {{Q_{m}\left( \frac{dV}{dq} \right)}_{{SOC}_{n}} = {Q_{m}\frac{{OCV_{{SOC}_{n} - t_{end}}} - {OCV_{{SOC}_{n} - t_{start}}}}{q_{{SOC}_{n}}^{\prime}}}}},$

where SOC_(n)−t_(start) represents the start moment of the SOC intervalof SOC_(n), SOC_(n)−t_(end) represents the end moment of the SOCinterval of SOC_(n), OCV_(SOC) _(n) _(−t) _(end) , represents an OCV atSOC_(n)−t_(start), OCV_(SOC) _(n) _(−t) _(start) represents an OCV atSOC_(n)−t_(end), and q′_(SOC) _(n) represents a partial dischargecapacity in the SOC interval of SOC_(n).

With reference to the seventh aspect, it should be noted that thedV/dSOC-SOC characteristic function includes:

${{g_{0}\left( {SOC}_{n} \right)} = {a_{0} + {\sum\limits_{j = 1}^{6}\left( {{a_{j}*{\sin \left( {j*\omega*SOC_{n}} \right)}} + {b_{j}*{\cos \left( {j*\omega*SOC_{n}} \right)}}} \right)}}},$

where SOC_(n) represents the n^(th) SOC, SOC_(n) is an independentvariable of the dV/dSOC-SOC characteristic function, g₀(SOC_(n))represents second dV/dSOC data corresponding to SOC_(n), j represents anorder, a₀, a_(j), and b_(j) are coefficients of terms, sin( ) representsa sine function, cos( ) represents a cosine function, and co representsfrequency.

With reference to the seventh aspect, optionally, the calculation moduleis specifically configured to:

calculate the m^(th) overall dV/dSOC data deviation of the plurality ofSOCs based on the first dV/dSOC data of each SOC in the m^(th) presetbattery capacity and the second dV/dSOC data corresponding to each SOCand with reference to a third preset formula, where the third presetformula includes:

${G_{m} = {\sum\limits_{n = 1}^{N}\left( {{g_{0}\left( {{SO}C_{n}} \right)} - {g_{1}\left( {{SO}C_{n}} \right)}} \right)^{2}}},$

where N represents the quantity of SOCs, N is a positive integer notless than 2, SOC_(n) represents the n^(th) SOC, g₀(SOC) represents thesecond dV/dSOC data corresponding to SOC_(n), g₁(SOC_(n)) represents thefirst dV/dSOC data of SOC_(n) in the m^(th) preset battery capacity, andG_(m) represents the m^(th) overall dV/dSOC data deviation of theplurality of SOCs.

According to an eighth aspect, an embodiment of this applicationdiscloses an apparatus for estimating a battery SOH, including aprocessor, a memory, a bus, and a communications interface. The memoryis configured to store a computer execution instruction. The processoris connected to the memory by using the bus. When the apparatus runs,the processor executes the computer execution instruction stored in thememory, so that the apparatus performs the method for estimating abattery SOH in the sixth aspect.

According to a ninth aspect, an embodiment of this application providesa computer-readable storage medium, configured to store a computersoftware instruction used by the foregoing apparatus for estimating abattery SOH. When the computer software instruction runs on a computer,the computer can perform the method for estimating a battery SOH in anypossible design of the sixth aspect.

According to a tenth aspect, an embodiment of this application providesa computer program product that includes an instruction. When thecomputer program product runs on a computer, the computer can performthe method for estimating a battery SOH in any possible design of thesixth aspect.

These aspects or other aspects of this application are clearer and morecomprehensible in descriptions of the following embodiments.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic architectural diagram of a system for estimating abattery SOH according to an embodiment of this application;

FIG. 2 is a schematic diagram of a hardware structure of an apparatusfor estimating a battery SOH according to an embodiment of thisapplication;

FIG. 3 is a schematic flowchart of a method for estimating a battery SOHaccording to an embodiment of this application;

FIG. 4 is a voltage-capacity line graph of charging or discharging atarget battery based on a preset current in a new battery state and atdifferent aging degrees according to an embodiment of this application;

FIG. 5 is a V-SOC line graph, corresponding to FIG. 4, of charging ordischarging a target battery based on a preset current in a new batterystate and at different aging degrees according to an embodiment of thisapplication;

FIG. 6 shows dV/dSOC characteristic curves of charging or discharging atarget battery based on a preset current in a new battery state and atdifferent aging degrees according to an embodiment of this application;

FIG. 7 is a schematic diagram of comparing a fitted curve with an actualcurve according to an embodiment of this application;

FIG. 8 is a schematic structural diagram of an apparatus for estimatinga battery SOH according to an embodiment of this application; and

FIG. 9 is a schematic structural diagram of another apparatus forestimating a battery SOH according to an embodiment of this application.

DESCRIPTION OF EMBODIMENTS

To facilitate understanding of the technical solutions in theembodiments of this application, explanations of several key terms arefirst provided as follows:

Retention capacity: a full charge or discharge capacity that is of abattery and that is obtained after the battery is used for a period oftime or left unused for a long period of time.

Aging: a phenomenon that a battery capacity naturally attenuates when abattery is used for a period of time or left unused for a long period oftime. Specifically, aging of a battery generally includes two parts:aging in a cycle process (namely, a cycle life), and aging in a processin which the battery is left unused (namely, a calendar life). The agingin the cycle process means that as a quantity of times ofcharging/discharging the battery increases, an available quantity oftimes that the battery can be charged/discharged decreasescorrespondingly, where a total quantity of times of charging/dischargingthe battery is measurable and can be estimated; and a retention capacityduring each time of charging/discharging attenuates. The aging in theprocess in which the battery is left unused means that when the batteryis not charged/discharged, a retention capacity of the batteryattenuates with time. A form of the aging in the embodiments of thisapplication is not limited. Uniform description is provided herein, anddetails are not described below again.

A new battery state (beginning of life, BOL) is specifically a batterystate in which a retention capacity is 100%.

State of health (SOH): a percentage of a retention capacity of an agedbattery in a capacity of a battery in a new battery state is defined asa battery SOH.

State of charge (SOC): the SOC is a ratio of a remaining capacity of abattery to a full charge capacity of the battery, and is usuallyexpressed as a percentage.

Open circuit voltage (OCV): a terminal voltage of a battery in an opencircuit state is referred to as the open circuit voltage.

Battery polarization: a phenomenon that an actual electrode potentialdeviates from a balanced electrode potential after a static state isbroken due to current flow.

The following describes the technical solutions in the embodiments ofthis application with reference to the accompanying drawings in theembodiments of this application. In the descriptions of thisapplication, unless otherwise stated, “I” indicates “or”, for example,A/B may indicate A or B; and “and/or” in this specification describesmerely an association relationship for describing associated objects,and indicates that three relationships may exist. For example, A and/orB may indicate the following three cases: Only A exists, both A and Bexist, and only B exists. In addition, in the descriptions of thisapplication, “a plurality of” means “two or more”.

FIG. 1 shows a system 10 for estimating a battery SOH according to anembodiment of this application. The system 10 for estimating a batterySOH includes a battery 20, a battery detection apparatus 21, acharging/discharging execution apparatus 22, an absolute-time unit 23, acontroller 24, a storage chip 25, and an apparatus 26 for estimating abattery SOH.

The battery detection apparatus 21 is configured to upload data that isdetected in real time to the controller. The battery detection apparatus21 includes three parts: a battery voltage sampling component, a currentsampling unit, and a temperature sampling component. The battery voltagesampling component includes a sampling chip and a connection bundle. Thecurrent sampling unit includes a current sampling chip and a currentsensor. The temperature sampling component includes a temperaturesampling chip and a temperature sensor.

The charging/discharging execution apparatus 22 is configured tocharge/discharge the battery.

The absolute-time unit 23 is configured to send, to the controller 24 inreal time, an absolute time provided by a high-frequency crystaloscillator.

The controller 24 is configured to: control sampling for the battery,receive the absolute time, and pack sampled data and the absolute timeand then store the packed sampled data and absolute time in the storagechip 25; and control a charge/discharge current and a state of thebattery by using the charging/discharging execution apparatus 22.

The storage chip 25 is configured to: prestore dV/dSOC-SOC informationof a new battery, and store collected valid battery data in real timeand in a particular format.

The apparatus 26 for estimating a battery SOH is configured to: performan ordered storage and read operation on data in the storage chip 25,and estimate a battery SOH based on the read data. For a specificimplementation, refer to the following method embodiment, and detailsare not described herein.

The system 10 for estimating a battery SOH may further include a powersupply, a security protection apparatus, an insulation apparatus, andthe like although they are not shown. This is not specifically limitedin this embodiment of this application.

FIG. 2 is a schematic diagram of a hardware structure of an apparatus 26for estimating a battery SOH according to an embodiment of thisapplication. The apparatus 26 for estimating a battery SOH includes atleast one processor 2601, a communications bus 2602, a memory 2603, andat least one communications interface 2604.

The processor 2601 may be a general-purpose central processing unit(CPU), a microprocessor, an application-specific integrated circuit(ASIC), or one or more integrated circuits configured to control programexecution of the solutions in this application.

The communications bus 2602 may include a channel for transmittinginformation between the foregoing components.

The communications interface 2604 is configured to use any apparatuslike a transceiver to communicate with another device or acommunications network, such as the Ethernet, a radio access network(RAN), or a wireless local area network (WLAN).

The memory 2603 may be a read-only memory (ROM) or another type ofstatic storage device capable of storing static information andinstructions, or a random access memory (RAM) or another type of dynamicstorage device capable of storing information and instructions, or maybe an electrically erasable programmable read-only memory (EEPROM), acompact disc read-only memory (CD-ROM) or another compact disc storage,an optical disc storage (including a compressed optical disc, a laserdisc, an optical disc, a digital versatile disc, a Blu-ray optical disc,and the like), a magnetic disk storage medium or another magneticstorage device, or any other medium capable of carrying or storingexpected program code in a form of an instruction or a data structureand capable of being accessed by a computer. However, the memory 2603 isnot limited thereto. The memory may exist independently, and isconnected to the processor by using the bus. Alternatively, the memorymay be integrated with the processor.

The memory 2603 is configured to store application program code forexecuting the solutions in this application, and the processor 2601controls the execution. The processor 2601 is configured to execute theapplication program code stored in the memory 2603, to implement themethod for estimating a battery SOH that is provided in the embodimentsof this application.

During specific implementation, in an embodiment, the processor 2601 mayinclude one or more CPUs, for example, a CPU 0 and a CPU 1 in FIG. 2.

During specific implementation, in an embodiment, the apparatus 26 forestimating a battery SOH may include a plurality of processors, forexample, the processor 2601 and a processor 2608 in FIG. 2. Each of theprocessors may be a single-core (single-CPU) processor, or may be amulti-core (multi-CPU) processor. The processor herein may be one ormore devices, circuits, and/or processing cores for processing data(e.g., a computer program instruction).

During specific implementation, in an embodiment, the apparatus 26 forestimating a battery SOH may further include an output device 2605 andan input device 2606. The output device 2605 communicates with theprocessor 2601, and can display information in a plurality of manners.For example, the output device 2605 may be a liquid crystal display(LCD), a light emitting diode (LED) display device, a cathode-ray tube(CRT) display device, or a projector. The input device 2606 communicateswith the processor 2601, and can receive a user input in a plurality ofmanners. For example, the input device 2606 may be a mouse, a keyboard,a touchscreen device, or a sensing device.

FIG. 3 shows a method for estimating a battery SOH according to anembodiment of this application. The method includes the following steps.

S301. An apparatus for estimating a battery SOH obtains a partial chargeor discharge capacity of a target battery in a SOC interval of each of aplurality of SOCs.

The SOC interval of each SOC is an interval whose start SOC is the SOCand whose length is dSOC.

S302. When determining that there are M preset battery capacities, theapparatus for estimating a battery SOH separately calculates, accordingto steps S1 to S3, an overall dV/dSOC data deviation corresponding toeach preset battery capacity, where M is a positive integer.

S1. The apparatus for estimating a battery SOH separately calculatesfirst dV/dSOC data of each SOC in an m^(th) preset battery capacitybased on the m^(th) preset battery capacity and the partial charge ordischarge capacity in the SOC interval of each SOC.

m is a positive integer less than or equal to M.

S2. The apparatus for estimating a battery SOH separately calculates,based on a prestored dV/dSOC characteristic function, second dV/dSOCdata corresponding to each SOC.

The dV/dSOC characteristic function is obtained by charging ordischarging the target battery based on a preset current in a newbattery state, the preset current is not greater than 1/20 Q_(BOL), andQ_(BOL) indicates a retention capacity of the target battery in the newbattery state.

S3. The apparatus for estimating a battery SOH calculates an m^(th)overall dV/dSOC data deviation of the plurality of SOCs based on thefirst dV/dSOC data of each SOC in the m^(th) preset battery capacity andthe second dV/dSOC data corresponding to each SOC.

S303. The apparatus for estimating a battery SOH determines a smallestoverall dV/dSOC data deviation from all overall dV/dSOC data deviations.

S304. The apparatus for estimating a battery SOH determines a presetbattery capacity corresponding to the smallest overall dV/dSOC datadeviation as a retention capacity of an aged target battery.

S305. The apparatus for estimating a battery SOH divides the retentioncapacity of the aged target battery by a retention capacity of thetarget battery in a new battery state, to obtain an SOH of the targetbattery.

In step S301:

The SOC interval of each SOC is an interval whose start SOC is the SOCand whose length is dSOC. For example, a SOC interval of a first SOC isan interval whose start SOC is the first SOC and whose length is dSOC.All SOCs intervals may have same dSOC, or may have different dSOC. Thisis not specifically limited in this embodiment of this application.

It should be noted that, for ease of representation, in this embodimentof this application, the first SOC is denoted as SOC₁, a second SOC isdenoted as SOC₂, and an n^(th) SOC is denoted as SOC_(n). This isuniformly described herein, and details are not described below again.

Optionally, the obtaining, by an apparatus for estimating a battery SOH,a partial charge or discharge capacity of a target battery in a SOCinterval of each of a plurality of SOCs may specifically include:obtaining, by the apparatus for estimating a battery SOH, the partialcharge or discharge capacity of the target battery in the SOC intervalof each of the plurality of SOCs with reference to formula (1). Formula(1) is as follows:

q _(SOC) _(n) =η∫_(SOC) _(n) _(−t) _(start) ^(SOC) ^(n) ^(−t) ^(end)i(t)SOC_(n) dt  formula (1)

SOC_(n) represents the n^(th) SOC. q_(SOC) _(n) represents a partialcharge or discharge capacity in a SOC interval of SOC_(n), η iscoulombic efficiency of the target battery, 0≤η≤1, and η may be givenbased on a battery type. For a lithium-ion battery, η may be 1. Foranother type of battery such as a lead-acid battery, a NiMH battery, ora Ni—Cd battery, η may be a value from 0.9 to 1 based on a differenttype. SOC_(n)−t_(start) represents a start moment of the SOC interval ofSOC_(n). SOC_(n)−t_(end) represents an end moment of the SOC interval ofSOC_(n). i(t) SOC_(n), represents a random current in the SOC intervalof SOC_(n).

For example, when the target battery works in a charge state, for theSOC interval of each SOC, when a charge current of the target battery isless than a preset value, for example, when in a large-current chargeprocess, a current in an initial charge phase and a current in an endcharge phase are controlled to be less than 1/20 Q_(BOL) or a current inthe entire charge process is controlled to be less than 1/20 Q_(BOL) thebattery detection apparatus 21 in FIG. 1 may flush all collected datainto the storage chip 25 in a form of a structure array. The structureincludes several array elements, such as a voltage, a current, atemperature, an absolute time, and an initial SOC, and may bespecifically represented as Data (k) {V[ ], I[ ], Temp[ ], Time[ ], SOC[]}, where k is a natural number from 0 to K and represents K pieces ofstructure data. Recording frequency is recorded based on samplingfrequency, and recording duration is Δt=t_(end)−t_(start). Then, theapparatus for estimating a battery SOH may read the foregoing structuredata from the storage chip 25, and then obtain a partial charge capacityof the target battery in the SOC interval of each of the plurality ofSOCs with reference to formula (1).

For example, when the target battery works in a discharge state, for theSOC interval of each SOC, when the target battery is in an approximateopen-circuit stable state, the battery detection apparatus 21 in FIG. 1may flush all collected data into the storage chip 25 in a form of astructure array. The structure includes several array elements, such asa voltage, a current, a temperature, an absolute time, and an initialSOC, and may be specifically represented as Data (k) {V[ ], I[ ], Temp[], Time[ ], SOC[ ]}, where k is a natural number from 0 to K andrepresents K pieces of structure data. Recording frequency is recordedbased on sampling frequency, and recording duration isΔt=t_(end)−t_(start). Then, the apparatus for estimating a battery SOHmay read the foregoing structure data from the storage chip 25, and thenobtain a partial discharge capacity of the target battery in the SOCinterval of each of the plurality of SOCs with reference to formula (1).In this embodiment of this application, if a current value I of thetarget battery is greater than −β and is less than β and this lasts γminutes, or the target battery is left unused in an open circuit formore than 15 minutes, it is considered that the target battery reachesthe approximate open-circuit stable state. Values of β and γ aredetermined based on a characteristic of the target battery. Generally, βis 2 A, and γ is 5 to 10 minutes.

For example, for SOC₁, the apparatus for estimating a battery SOH mayread K pieces of structure data in a SOC interval of SOC₁ from thestorage chip 25, and obtain a partial charge or discharge capacity inthe SOC interval of SOC₁ according to formula (1). The partial charge ordischarge capacity in the SOC interval of SOC₁ is as follows:

$q_{{SOC}_{1}} = {{\eta {\int_{{SOC_{1}} - t_{start}}^{{SOC_{1}} - t_{end}}{{i(t)}_{SOC_{1}}dt}}} = {\eta {\sum\limits_{k = 0}^{K}{I\lbrack k\rbrack}_{SOC_{1}}}}}$

It should be noted that in this embodiment of this application, a valueof K depends on an absolute time t, an absolute time t_(start) is anabsolute moment at which data is recorded at the beginning of analgorithm, an absolute time t_(end) is an absolute moment at which anSOH starts to be estimated at the end of the algorithm, and a timedifference between t_(start) and t_(end) is usually not more than onemonth. In addition, the value of K cannot exceed a preset upper limitvalue. For example, the preset upper limit value is 100, and thisindicates that data recording is performed for a maximum of one hundredtimes. The preset upper limit value may be determined based on a size ofthe storage chip 25. When storage permission is met, a larger presetupper limit value indicates a larger amount of data participating inestimation and higher estimation accuracy.

In S1 of step S302:

Optionally, the separately calculating, by the apparatus for estimatinga battery SOH, first dV/dSOC data of each SOC in an m^(th) presetbattery capacity based on the m^(th) preset battery capacity and thepartial charge or discharge capacity in the SOC interval of each SOC mayspecifically include: separately calculating, by the apparatus forestimating a battery SOH, the first dV/dSOC data of each SOC in them^(th) preset battery capacity based on the m^(th) preset batterycapacity and the partial charge or discharge capacity in the SOCinterval of each SOC and with reference to formula (2). Formula (2) isas follows:

$\begin{matrix}{{g_{1}\left( {SOC_{n}} \right)} = {Q_{m}\left( \frac{dV}{dq} \right)}_{{SOC}_{n}}} & {{formula}\mspace{14mu} (2)}\end{matrix}$

Q_(m) represents the m^(th) preset battery capacity, SOC_(n) representsthe n^(th) SOC, g₁(SOC_(n)) represents first dV/dSOC data of SOC_(n) inthe m^(th) preset battery capacity, V represents a voltage, q representsa partial charge or discharge capacity, and

$\left( \frac{dV}{dq} \right)_{{SOC}_{n}}$

represents

$\frac{dV}{dq}$

corresponding to SOC_(n).

For example, assuming that the apparatus for estimating a battery SOHcan read K pieces of structure data in the SOC interval of SOC_(n) fromthe storage chip 25, because a V-SOC curve is linear in a short periodof time, the apparatus for estimating a battery SOH may calculate thefirst dV/dSOC data of SOC_(n) in the m^(th) preset battery capacityaccording to formula (2). The first dV/dSOC data of SOC_(n) in them^(th) preset battery capacity is as follows:

${g_{1}\left( {SOC}_{n} \right)} = {{Q_{m}\left( \frac{dV}{dq} \right)}_{{SOC}_{n}} = {{Q_{m}\frac{V_{{SOC}_{n} - t_{end}} - V_{{SOC}_{n} - t_{start}}}{\;_{q_{{SOC}_{n}}}}} = {Q_{m}\frac{{V\lbrack K\rbrack}_{{SOC}_{n}} - {V\lbrack 0\rbrack}_{{SOC}_{n}}}{q_{{SOC}_{n}}}}}}$

SOC_(n)−t_(start) represents the start moment of the SOC interval ofSOC_(n), SOC_(n)−t_(end) represents the end moment of the SOC intervalof SOC_(n), V[K]_(SOC) _(n) _(−t) _(end) represents a voltage atSOC_(n)−t_(end), V_(SOC) _(n) _(−t) _(start) represents a voltage atSOC_(n)−t_(start), V[K]_(SOC) _(n) represents a K^(th) voltage in theSOC interval of SOC_(n), and V[0]_(SOC) _(n) , represents an initialvoltage in the SOC interval of SOC_(n).

Optionally, when the target battery works in a discharge state, afterthe target battery is stable and static for a period of time, or aworking condition of the target battery keeps at a very small currentfor a period of time, it can be considered that battery polarizationdisappears. In this case, a terminal voltage V of the target battery atan initial moment can be considered as an OCV of the target battery atthe initial moment. In addition, because an OCV-SOC curve is linear in ashort period of time, it can be learned that dq is proportional to dOCVin a short period of time. Therefore, when the target battery works inthe discharge state, the foregoing formula (2) can be evolved into thefollowing formula (3):

$\begin{matrix}{{g_{1}\left( {SOC}_{n} \right)} = {{Q_{m}\left( \frac{dV}{dq} \right)}_{{SOC}_{n}} = {Q_{m}\frac{{OCV}_{{SOC}_{n} - t_{end}} - {OCV}_{{SOC}_{n} - t_{start}}}{q_{{SOC}_{n}}^{\prime}}}}} & {{formula}\mspace{14mu} (3)}\end{matrix}$

OCV_(SOC) _(n) _(−t) _(end) represents an OCV at SOC_(n)−t_(start),OCV_(SOC) _(n) _(−t) _(start) represents an OCV at SOC_(n)−t_(start),and q′_(SOC) represents a partial discharge capacity in the SOC intervalof SOC_(n).

Optionally, the apparatus for estimating a battery SOH may determineOCV_(t) and OCV_(SOC) _(n) _(−t) _(end) based on a start SOC and an endSOC of the SOC interval of SOC_(n) and with reference to a prestoredcorrespondence between a SOC and an OCV. This is not specificallylimited in this embodiment of this application.

For example, assuming that the apparatus for estimating a battery SOHcan read the K pieces of structure data in the SOC interval of SOC_(n)from the storage chip 25, the apparatus for estimating a battery SOH maycalculate the first dV/dSOC data in the m^(th) preset battery capacityaccording to formula (3). The first dV/dSOC data in the m^(th) presetbattery capacity is as follows:

${g_{1}\left( {SOC}_{n} \right)} = {{Q_{m}\left( \frac{dV}{dq} \right)}_{{SOC}_{n}} =  {{Q_{m}\left( \frac{{OCV}_{{SOC}_{n} - t_{end}} - {OCV}_{{SOC}_{n} - t_{start}}}{q_{{SOC}_{n}}^{\prime}} \right)}_{m} \frac{{{OCV}\lbrack K\rbrack}_{{SOC}_{n}} - {{OCV}\lbrack 0\rbrack}_{{SOC}_{n}}}{q_{{SOC}_{n}}^{\prime}}}}$

OCV[K]_(SOC) _(n) represents a K^(th) OCV in the SOC interval ofSOC_(n), and OCV[0]_(SOC) _(n) represents an initial OCV in the SOCinterval of SOC_(n). OCV[K]_(SOC) _(n) can be determined based onSOC_(n)[K] and the prestored correspondence between a SOC and an OCV,and OCV[0]_(SOC) _(n) can be determined based on SOC_(n)[0] and theprestored correspondence between a SOC and an OCV. SOC_(n)[K] representsa K^(th) SOC in the SOC interval of SOC_(n), and SOC_(n)[0] representsan initial SOC in the SOC interval of SOC_(n).

In S2 of step S302:

That the apparatus for estimating a battery SOH separately calculates,based on a prestored dV/dSOC characteristic function, second dV/dSOCdata corresponding to each SOC is specifically that the apparatus forestimating a battery SOH separately substitutes each SOC to theprestored dV/dSOC characteristic function to obtain the second dV/dSOCdata corresponding to each SOC.

Optionally, the prestored dV/dSOC characteristic function may beobtained in the following manner:

Step 1: Charge or discharge the target battery based on a preset currentin a new battery state, to obtain a voltage-capacity curve.

The preset current is not greater than 1/20 Q_(BOL). For example, thepreset current is 1/25 Q_(BOL).

For example, FIG. 4 is a voltage-capacity (V-Q) line graph of chargingor discharging the target battery based on the preset current in the newbattery state and at different aging degrees according to thisembodiment of this application. A curve 1 is a V-Q line graph ofcharging or discharging the target battery based on the preset currentin the new battery state. A curve 2 is a V-Q line graph of charging ordischarging the target battery based on the preset current at an agingdegree of 400 cycles. A curve 3 is a V-Q line graph of charging ordischarging the target battery based on the preset current at an agingdegree of 1000 cycles. A curve 4 is a V-Q line graph of charging ordischarging the target battery based on the preset current at an agingdegree of 2000 cycles. It can be seen from FIG. 4 that a capacity thatcan be released by the target battery decreases gradually as an agingdegree increases, in other words, as a quantity of cycle timesincreases, and V-Q curves have an obvious deviation at the end ofdischarging.

It should be noted that, because a voltage in a small-current conditionvery approximates to an OCV, the voltage-capacity curve in thisembodiment of this application very approximates to an existingOCV-capacity curve. This is uniformly described herein, and details arenot described below again.

Step 2: Convert the voltage-capacity curve into a voltage-state ofcharge (V-SOC) curve.

A charge/discharge capacity of the target battery is converted into aratio of a remaining capacity of the target battery to a full chargecapacity of the target battery based on the voltage-capacity curveobtained in step 1 and according to a definition of the SOC, to obtainthe V-SOC curve.

For example, FIG. 5 is a V-SOC line graph, corresponding to FIG. 4, ofcharging or discharging the target battery based on the preset currentin the new battery state and at the different aging degrees. It can beseen from FIG. 5 that, when charging or discharging is performed basedon the preset current, V-SOC curves at different aging degrees present anormalization characteristic. In this embodiment of this application,the battery SOH is estimated based on this normalization characteristic.

Step 3: Obtain a dV/dSOC characteristic curve of the target batterybased on the V-SOC curve.

For example, dV/dSOC characteristic curves of charging or dischargingthe target battery based on the preset current in the new battery stateand at the different aging degrees may be shown in FIG. 6.

Step 4: Extract points on the dV/dSOC characteristic curve for fitting,to obtain the dV/dSOC characteristic function of the target battery inthe new state.

For example, points in an interval with a highest curve normalizationdegree in FIG. 6 may be selected for fitting. For example, points in aSOC interval from 0 to 0.7 are selected for fitting.

When charging or discharging is performed based on the preset current,the V-SOC curves at the different aging degrees present thenormalization characteristic. Therefore, when charging or discharging isperformed based on the preset current, the dV/dSOC characteristicfunction that is of the target battery in the new state and that isobtained by charging or discharging the target battery based on thepreset current in the new battery state may also be considered as adV/dSOC characteristic function of the target battery at the differentaging degrees.

For example, the dV/dSOC characteristic function may be shown as formula(4):

$\begin{matrix}{{g_{0}\left( {SOC}_{n} \right)} = {a_{0} + {\sum\limits_{j = 1}^{6}\left( {{a_{j}*{\sin \left( {j*\omega*{SOC}_{n}} \right)}} + {b_{j}*{\cos \left( {j*\omega*{SOC}_{n}} \right)}}} \right)}}} & {{formula}\mspace{14mu} (4)}\end{matrix}$

The characteristic function is a six-order Fourier function. SOC_(n) isan independent variable of the dV/dSOC characteristic function.g₀(SOC_(n)) represents second dV/dSOC data corresponding to SOC_(n). jrepresents an order, a₀, a_(j), and b_(j) are coefficients of terms, andthe order and the coefficients are all obtained by using a fitting tool.sin( ) represents a sine function. cos( ) represents a cosine function.ω represents frequency.

FIG. 7 is a schematic diagram of comparing a fitted curve correspondingto the dV/dSOC characteristic function shown in formula (4) with anoriginal dV/dSOC characteristic curve, and the two curves basicallycoincide.

Optionally, in this embodiment of this application, when the dV/dSOCcharacteristic function is fitted by using a fitting tool, the fittingis performed by using an example in which the characteristic function isthe six-order Fourier function. Certainly, in practice, thecharacteristic function may further include but is not limited only to apolynomial function, a Fourier function, an exponential function, andthe like. This is not specifically limited in this embodiment of thisapplication.

In S3 of step S302:

Optionally, the calculating, by the apparatus for estimating a batterySOH, an m^(th) overall dV/dSOC data deviation of the plurality of SOCsbased on the first dV/dSOC data of each SOC in the m^(th) preset batterycapacity and the second dV/dSOC data corresponding to each SOCspecifically includes: calculating, by the apparatus for estimating abattery SOH, the m^(th) overall dV/dSOC data deviation of the pluralityof SOCs based on the first dV/dSOC data of each SOC in the m^(th) presetbattery capacity and the second dV/dSOC data corresponding to each SOCand with reference to formula (5). Formula (5) includes:

$\begin{matrix}{G_{m} = {\sum\limits_{n = 1}^{N}\left( {{g_{0}\left( {SOC}_{n} \right)} - {g_{1}\left( {SOC}_{n} \right)}} \right)^{2}}} & {{formula}\mspace{14mu} (5)}\end{matrix}$

N represents a quantity of SOCs, N is a positive integer not less than2, and G_(m) represents the m^(th) overall dV/dSOC data deviation of theplurality of SOCs.

For example, g₁(SOC) may be shown as formula (2), g₀(SOC) may be shownas formula (4), and the following formula (6) can be obtained bysubstituting formula (2) and formula (4) into formula (5):

$\begin{matrix}{G_{m} = {{\sum\limits_{n = 1}^{N}\left( {{g_{0}\left( {SOC}_{n} \right)} - {g_{1}\left( {SOC}_{n} \right)}} \right)^{2}} = \begin{matrix}{\sum\limits_{n = 1}^{N}\; \left( {\left( {a_{0} + {\sum\limits_{j = 1}^{6}\; \left( {{a_{j}*{\sin \left( {j*\omega*{SOC}_{n}} \right)}} + {b_{j}*{\cos \left( {j*\omega*{SOC}_{n}} \right)}}} \right)}} \right) - {Q_{m}\left( \frac{dV}{dq} \right)}_{{SOC}_{n}}} \right)^{2}} \\\square\end{matrix}}} & {{formula}\mspace{14mu} (6)}\end{matrix}$

It can be learned that G_(m) is related to Q_(m). Table 1 provides agroup of mapping relationships between G_(m) and Q_(m), as shown below:

TABLE 1 Q Q_(EOL) Q₁ . . . . . . Q_(m) . . . Q_(BOL) G G₀ G₁ . . . . . .G_(m) . . . G_(M)

Q_(EOL) represents a full charge/full discharge capacity of the targetbattery at the end of life (EOL), and Q_(BOL) represents a fullcharge/full discharge capacity of the target battery in the new batterystate.

In step S303:

The apparatus for estimating a battery SOH may determine the smallestoverall dV/dSOC data deviation from all the overall dV/dSOC datadeviations in a sorting manner, or may determine the smallest overalldV/dSOC data deviation from all the overall dV/dSOC data deviations inanother manner. This is not specifically limited in this embodiment ofthis application.

In step S304:

The apparatus for estimating a battery SOH determines the preset batterycapacity corresponding to the smallest overall dV/dSOC data deviation asthe retention capacity of the aged target battery. It can be learnedfrom the foregoing descriptions that the dV/dSOC characteristic functionthat is of the target battery in the new state and that is obtained bycharging or discharging the target battery based on the preset currentin the new battery state may also be considered as the dV/dSOCcharacteristic function of the target battery at the different agingdegrees. Therefore, theoretically, the preset battery capacitycorresponding to the smallest overall dV/dSOC data deviation mostapproximates to an estimated capacity value of an actual retentioncapacity.

In step S305:

According to a definition of the SOH, the SOH of the target battery canbe obtained only by dividing the retention capacity of the aged targetbattery by the retention capacity of the target battery in the newbattery state.

In the method for estimating a battery SOH that is provided in thisembodiment of this application, the apparatus for estimating a batterySOH obtains the partial charge or discharge capacity of the targetbattery in the SOC interval of each of the plurality of SOCs; separatelycalculates the first dV/dSOC data of each SOC in the m^(th) presetbattery capacity based on the m^(th) preset battery capacity and thepartial charge or discharge capacity in the SOC interval of each SOC;separately calculates, based on the prestored dV/dSOC characteristicfunction, the second dV/dSOC data corresponding to each SOC, where thedV/dSOC characteristic function is obtained by charging or dischargingthe target battery based on the preset current in the new battery state,the preset current is not greater than 1/20 Q_(BOL), and Q_(BOL)indicates the retention capacity of the target battery in the newbattery state; calculates the m^(th) overall dV/dSOC data deviation ofthe plurality of SOCs based on the first dV/dSOC data of each SOC in them^(th) preset battery capacity and the second dV/dSOC data correspondingto each SOC; determines the smallest overall dV/dSOC data deviation fromall the overall dV/dSOC data deviations; determines the preset batterycapacity corresponding to the smallest overall dV/dSOC data deviation asthe retention capacity of the aged target battery; and determines theSOH of the target battery based on the retention capacity of the agedtarget battery. In other words, in this solution, the retention capacityof the aged target battery is estimated based on the partial charge ordischarge capacity in the SOC interval of each SOC. In this way, thissolution is unlike the prior art in which the parameter can be obtainedonly by performing one full charge or full discharge test, and thereforean implementation condition of this solution is simpler and moreflexible. In addition, this solution does not need to rely on historicaldata, and therefore is more robust.

The actions of the apparatus for estimating a battery SOH in theforegoing steps S301 to S305 may be performed by the processor 2601 inthe apparatus 26 for estimating a battery SOH that is shown in FIG. 2,by invoking the application program code stored in the memory 2603. Thisis not limited in this embodiment of this application.

The foregoing mainly describes the solutions provided in the embodimentsof this application from a perspective that the apparatus for estimatinga battery SOH performs the method for estimating a battery SOH. It maybe understood that to implement the foregoing functions, the apparatusfor estimating a battery SOH includes corresponding hardware structuresand/or software modules for performing the functions. A person skilledin the art should be very easily aware that, with reference to theexamples described in the embodiments disclosed in this specification,units and algorithm steps can be implemented in this application byhardware or a combination of hardware and computer software. Whether afunction is implemented by hardware or by computer software by drivinghardware depends on particular applications and design constraints ofthe technical solutions. A person skilled in the art may use differentmethods to implement the described functions for each particularapplication, but it should not be considered that the implementationgoes beyond the scope of this application.

In the embodiments of this application, functional modules of theapparatus for estimating a battery SOH may be obtained through divisionbased on the foregoing method examples. For example, each functionalmodule may be obtained through division for each corresponding function,or two or more functions may be integrated into one processing module.The integrated module may be implemented in a form of hardware, or maybe implemented in a form of a software function module. It should benoted that, in the embodiments of this application, module division ismerely an example and is merely logical function division. During actualimplementation, there may be another division manner.

For example, when each functional module is obtained through divisionfor each corresponding function, FIG. 8 is a possible schematicstructural diagram of an apparatus 80 for estimating a battery SOH inthe foregoing embodiment. The apparatus 80 for estimating a battery SOHincludes an obtaining module 801, a calculation module 802, and adetermining module 803. The obtaining module 801 is configured tosupport the apparatus 80 for estimating a battery SOH in performing stepS301 in FIG. 3. The calculation module 802 is configured to support theapparatus 80 for estimating a battery SOH in performing steps S302 andS305 in FIG. 3. The determining module 803 is configured to support theapparatus 80 for estimating a battery SOH in performing steps S303 andS304 in FIG. 3.

All related content of the steps in the foregoing method embodiment canbe cited in function descriptions of corresponding functional modules,and details are not described herein.

When each functional module is obtained through division in anintegration manner, FIG. 9 is a possible schematic structural diagram ofan apparatus 90 for estimating a battery SOH in the foregoingembodiment. As shown in FIG. 9, the apparatus 90 for estimating abattery SOH includes a processing module 901. The processing module 901is configured to support the apparatus 90 for estimating a battery SOHin performing steps S301 to S305 in FIG. 3.

All related content of the steps in the foregoing method embodiment canbe cited in function descriptions of corresponding functional modules,and details are not described herein.

In the embodiments of this application, the apparatus for estimating abattery SOH is presented in a form that each functional module isobtained through division for each corresponding function, or theapparatus for estimating a battery SOH is presented in a form that eachfunctional module is obtained through division in an integration manner.The “module” herein may be an application-specific integrated circuit(ASIC), a circuit, a processor that executes one or more software orfirmware programs and a memory, an integrated logic circuit, and/oranother component that can provide the foregoing functions. In a simpleembodiment, a person skilled in the art may consider that the apparatus80 for estimating a battery SOH or the apparatus 90 for estimating abattery SOH may use the form shown in FIG. 2. For example, the obtainingmodule 801, the calculation module 802, and the determining module 803in FIG. 8 may be implemented by the processor 2601 and the memory 2603in FIG. 2. Specifically, the obtaining module 801, the calculationmodule 802, and the determining module 803 may be implemented by theprocessor 2601 by invoking the application program code stored in thememory 2603. This is not limited in the embodiments of this application.Alternatively, for example, the processing module 901 in FIG. 9 may beimplemented by the processor 2601 and the memory 2603 in FIG. 2.Specifically, the processing module 901 may be implemented by theprocessor 2601 by invoking the application program code stored in thememory 2603. This is not limited in the embodiments of this application.

Because the apparatus for estimating a battery SOH that is provided inthe embodiments of this application may be configured to perform theforegoing method for estimating a battery SOH, for a technical effectthat can be obtained by the apparatus for estimating a battery SOH,refer to the foregoing method embodiment. Details are not describedherein again in the embodiments of this application.

All or some of the foregoing embodiments may be implemented by software,hardware, firmware, or any combination thereof. When a software programis used to implement the embodiments, all or some of the embodiments maybe implemented in a form of a computer program product. The computerprogram product includes one or more computer instructions. When thecomputer program instructions are loaded and executed on a computer, allor some of the procedures or functions according to the embodiments ofthis application are generated. The computer may be a general-purposecomputer, a dedicated computer, a computer network, or anotherprogrammable apparatus. The computer instructions may be stored in acomputer-readable storage medium or may be transmitted from acomputer-readable storage medium to another computer-readable storagemedium. For example, the computer instructions may be transmitted from awebsite, computer, server, or data center to another website, computer,server, or data center in a wired (e.g., a coaxial cable, an opticalfiber, or a digital subscriber line) or wireless (for example, infrared,radio, or microwave) manner. The computer-readable storage medium may beany usable medium accessible by a computer, or a data storage device,such as a server or a data center, integrating one or more usable media.The usable medium may be a magnetic medium (e.g., a floppy disk, a harddisk, or a magnetic tape), an optical medium (e.g., a DVD), asemiconductor medium (e.g., a solid state disk), or the like.

Although this application is described herein with reference to theembodiments, in a process of implementing this application that claimsprotection, a person skilled in the art may understand and implementanother variation of the disclosed embodiments by viewing theaccompanying drawings, the disclosed content, and the appended claims.In the claims, “comprising” does not exclude another component or step,and “a” or “one” does not exclude a case of “a plurality of”. A singleprocessor or another unit may implement several functions enumerated inthe claims. Some measures are recorded in appended claims that aredifferent from each other, but this does not mean that these measurescannot be combined to produce a better effect.

Although this application is described with reference to specificfeatures and the embodiments thereof, apparently, various modificationsand combinations may be made to this application without departing fromscope of this application. Correspondingly, the specification andaccompanying drawings are merely example descriptions of thisapplication defined by the appended claims, and are considered to coverany of or all modifications, variations, combinations, or equivalentswithin the scope of this application. Apparently, a person skilled inthe art can make various modifications and variations to thisapplication without departing from the spirit and scope of thisapplication. In this way, this application is intended to cover thesemodifications and variations of this application provided that they fallwithin the scope of the claims of this application and equivalenttechnologies thereof

What is claimed is:
 1. A method of estimating a state of health (SOH) ofa battery, comprising: obtaining a partial charge or discharge capacityof the battery in each of a plurality of state of charge (SOC) ranges;determining, based on the partial charge or discharge capacity of thebattery in each SOC range of the plurality of SOC ranges, an overalldV/dSOC data deviation corresponding to each of M preset batterycapacities of the battery to obtain overall dV/dSOC data deviationscorresponding to the M preset battery capacities, where M is a positiveinteger; and estimating the SOH of the battery based on a preset batterycapacity corresponding to a smallest overall dV/dSOC data deviation inthe overall dV/dSOC data deviations.
 2. The method according to claim 1,wherein the obtaining the partial charge or discharge capacity of thebattery in each of the plurality of SOC ranges, comprises: obtaining thepartial charge or discharge capacity of the battery in a first SOC rangebased on a coulombic efficiency of the battery, and a random currentbetween a start moment of the first SOC range and an end moment of thefirst SOC range, where the first SOC range is one of the plurality ofSOC ranges.
 3. The method according to claim 1, wherein each of theplurality of SOC ranges starts with an SOC of a plurality of SOCs. 4.The method according to claim 1, wherein the determining an overalldV/dSOC data deviation corresponding to each of M preset batterycapacities, comprises: obtaining, based on a first preset batterycapacity and the partial charge or discharge capacity of the battery ineach of the plurality of SOC ranges, a first dV/dSOC data, where thefirst preset battery capacity is one of the M preset battery capacities;obtaining, based on a dV/dSOC characteristic function and the firstdV/dSOC data, a second dV/dSOC data; and obtaining the overall dV/dSOCdata deviation corresponding to the first preset battery capacity basedon the first dV/dSOC data and the second dV/dSOC data.
 5. The methodaccording to claim 1, wherein the estimating the SOH of the batterybased on a preset battery capacity corresponding to a smallest overalldV/dSOC data deviation in the overall dV/dSOC data deviationscorresponding to the M preset battery capacities, comprises: determiningthe preset battery capacity corresponding to the smallest overalldV/dSOC data deviation as a retention capacity of the battery in an agedstate; and determining the SOH of the battery based on the retentioncapacity of the battery in the aged state and a retention capacity ofthe battery in a new battery state.
 6. An apparatus, comprising aprocessor; and a memory configured to store a computer executioninstructions, wherein the processor is configured execute the computerexecution instructions to carry out the following: obtaining a partialcharge or discharge capacity of a battery in each of a plurality ofstate of charge (SOC) ranges; determining, based on the partial chargeor discharge capacity of the battery in each SOC range, an overalldV/dSOC data deviation corresponding to each of M preset batterycapacities of the battery to obtain overall dV/dSOC data deviationscorresponding to the M preset battery capacities, where M is a positiveinteger; and estimating the SOH of the battery based on a preset batterycapacity corresponding to a smallest overall dV/dSOC data deviation inthe overall dV/dSOC data deviations.
 7. The apparatus according to claim6, wherein the obtaining the partial charge or discharge capacity of thebattery in each of the plurality of SOC ranges, comprises: obtaining thepartial charge or discharge capacity of the battery in a first SOC rangebased on a coulombic efficiency of the battery, and a random currentbetween a start moment of the first SOC range and an end moment of thefirst SOC rang, where the first SOC range is one of the plurality of SOCranges.
 8. The apparatus according to claim 6, wherein each of theplurality of SOC ranges starts with an SOC of a plurality of SOCs. 9.The apparatus according to claim 6, wherein the determining an overalldV/dSOC data deviation corresponding to each of M preset batterycapacities, comprises: obtaining, based on a first preset batterycapacity and the partial charge or discharge capacity of the battery ineach of the plurality of SOC ranges, a first dV/dSOC data, where thefirst preset battery capacity is one of the M preset battery capacities;obtaining, based on a dV/dSOC characteristic function and the firstdV/dSOC data, a second dV/dSOC data; and obtaining the overall dV/dSOCdata deviation corresponding to the first preset battery capacity basedon the first dV/dSOC data and the second dV/dSOC data.
 10. The apparatusaccording to claim 6, wherein the estimating the SOH of the batterybased on a preset battery capacity corresponding to a smallest overalldV/dSOC data deviation in the overall dV/dSOC data deviationscorresponding to the M preset battery capacities, comprises: determiningthe preset battery capacity corresponding to the smallest overalldV/dSOC data deviation as a retention capacity of the battery in an agedstate; and determining the SOH of the battery based on the retentioncapacity of the battery in the aged state and a retention capacity ofthe battery in a new battery state.
 11. A non-transitorycomputer-readable storage medium, comprising a program, wherein theprogram is configured to be executed by a processor to carry out thefollowing: obtaining a partial charge or discharge capacity of a batteryin each of a plurality of state of charge (SOC) ranges; determining,based on the partial charge or discharge capacity of the battery in eachSOC range, an overall dV/dSOC data deviation corresponding to each of Mpreset battery capacities of the battery to obtain overall dV/dSOC datadeviations corresponding to the M preset battery capacities, where M isa positive integer; and estimating the SOH of the battery based on apreset battery capacity corresponding to a smallest overall dV/dSOC datadeviation in the overall dV/dSOC data deviations.
 12. The non-transitorycomputer-readable storage medium according to claim 11, wherein theobtaining the partial charge or discharge capacity of the battery ineach of the plurality of SOC ranges, comprises: obtaining the partialcharge or discharge capacity of the battery in a first SOC range basedon a coulombic efficiency of the battery, and a random current between astart moment of the first SOC range and an end moment of the first SOCrange, where the first SOC range is one of the plurality of SOC ranges.13. The non-transitory computer-readable storage medium according toclaim 11, wherein each of the plurality of SOC ranges starts with an SOCof a plurality of SOCs.
 14. The non-transitory computer-readable storagemedium according to claim 11, wherein the determining an overall dV/dSOCdata deviation corresponding to each of M preset battery capacities,comprises: obtaining, based on a first preset battery capacity and thepartial charge or discharge capacity of the battery in each of theplurality of SOC ranges, a first dV/dSOC data, where the first presetbattery capacity is one of the M preset battery capacities; obtaining,based on a dV/dSOC characteristic function and the first dV/dSOC data, asecond dV/dSOC data; and obtaining the overall dV/dSOC data deviationcorresponding to the first preset battery capacity based on the firstdV/dSOC data and the second dV/dSOC data.
 15. The non-transitorycomputer-readable storage medium according to claim 11, wherein theestimating the SOH of the battery based on a preset battery capacitycorresponding to a smallest overall dV/dSOC data deviation in theoverall dV/dSOC data deviations corresponding to the M preset batterycapacities, comprises: determining the preset battery capacitycorresponding to the smallest overall dV/dSOC data deviation as aretention capacity of the battery in an aged state; and determining theSOH of the battery based on the retention capacity of the battery in theaged state and a retention capacity of the battery in a new batterystate.